Contents - Greenmount Press

FIGURe 4: Effect of off-season operations on establishment of solenopsis mealybug on early stage
cotton
season. Operations were targeted at controlling overwintering
hosts. Three treatments were tested. Each treatment involved a
combination of operations. The treatments were:
■■
Mulching, deep cultivation/pupae busting, light cultivation,
two herbicide applications (Roundup and Zulu and
Gramoxone) plus Cruiser treated seed.
■■
Mulching, deep cultivation/pupae busting plus Cruiser treated
seed.
■■
Mulching, deep cultivation/pupae busting plus untreated seed.
The paddock was mulched on May 18, 2011, following
picking. On August 6, the field was pupae busted. Herbicide was
applied twice to treatment 1. The cotton was planted on October
24. All treatments were assessed four times from emergence to
early boll setting stage (January 9).
Solenopsis mealybug is an emerging pest of cotton in
Australia.
The results are summarised in Figure 2. It clearly shows that
treatment 1 plots had a significantly lower solenopsis mealybug
population at the early stages of growth than treatments 2
and 3. The figure also shows that plots with treatment 2 had
significantly lower population than plots with treatment 3. The
only difference between treatment 2 and 3 was seed treatment.
This result suggests that seed treatment reduces the early
establishment of solenopsis mealybug on cotton.
Conclusions
Our study on the overwintering of solenopsis mealybug shows
that they can survive during winter, using whatever plant species
is available. They can survive in the soil for some time without
any plant host. This overwintering strategy makes solenopsis
mealybug a difficult pest to manage. But we have seen natural
enemies such as lady beetles and lacewings active in the field
during winter. Potentially these beneficials can keep solenopsis
mealybug under control, particularly if they are not killed by
insecticides targeted to control pests such as mirids.
Off-season operations trial results emphasise the importance
of farm hygiene (see The Australian Cottongrower 31 page 18-
22). Keeping fields clean after harvest until planting is critical
to reducing subsequent infestations of solenopsis mealybug.
Fields without any weed hosts or ratoon cotton will reduce early
establishment on cotton. In addition to farm operations, seed
treatment will also reduce solenopsis mealybug establishment
on seedling cotton. But it is not yet clear whether there are any
differences in effectiveness of seed treatments. A trial is planned
for this season to explore this.
We thank Michael and Andrea Stuart of Byee for allowing us to conduct the
trial in their property and for helping with the operations. We also thank
Adam Quade, DAFF, Toowoomba for helping with the trial. The Cotton
Research and Development Corporation provided funding (DAQ 1204)
1
DAFF Queensland, Toowoomba, Qld 4350.
2
DAFF Queensland, Emerald, Qld 4720.
3
CRDC, Emerald, Qld 4720.
24 — The Australian Cottongrower October–November 2012